In general, liquid crystal display (LCD) devices may provide advantages, such as improved screen definition, light weight, thin construction, and/or low power consumption when compared with cathode ray tube (CRT) display devices. Use of LCD devices is thus increasing relative to CRT display devices, and LCD devices are being used in mobile systems such as notebook computers, mobile communication terminals, television sets, computer systems, and various other applications.
Typically, these LCD devices may include an LCD panel, a driver used to drive the LCD panel, a timing controller, and other components. Furthermore, the driver may be configured as a chip to be more easily built-in within the LCD device, and the chip may be referred to as a display driver integrated circuit (DDI).
The driver of the LCD may be classified as a source driver used to apply data signals to display a picture to a plurality of data lines formed in the LCD panel, a gate driver used to apply drive signals to sequentially scan gate lines of the LCD panel, etc.
The gate driver may perform a function of sequentially supplying turn-on voltages of switching transistors through the gate lines so that the picture data provided from the source driver may be provided to each of the pixels formed at the intersections of the gate lines and source lines of the LCD panel.
FIG. 1 is a circuit diagram illustrating a conventional gate driver. Referring to FIG. 1, a conventional gate driver 10 may include a decoder 11 used to decode data provided from an exterior timing controller to output a decoded signal, a plurality of D-type flip-flops 12 used to receive each of the decoded signals output from the decoder 11 to generate output signals according to a divided clock CK applied from the exterior, and a plurality of buffers 14 used to buffer the output signals from the D-type flip-flops 12 to apply the final gate voltage through output pins P to the gate lines. In addition, a NAND gate 13 may be coupled between the D-type flip-flops 12 and the buffers 14.
As illustrated in FIG. 1, the data signal supplied from the exterior may be an n-bit data signal. Therefore, the number of the signals decoded by the decoder may be 2n, and the number of the D-type flip-flops and the buffers may be 2n. Accordingly, each of 2n gate voltage signals may be output through each of 2n output pins P in response to the input n-bit data signal.
As LCD panels have been gradually increasing in size, a number of output pins of the semiconductor devices including the driver integrated circuit (IC) used to drive the LCD panel have been increasing.
Accordingly, providing adequate quality is an increasingly important issue in the semiconductor devices, and research on test techniques for the semiconductor devices has been in progress. Improved test processes may be needed because errors that may occur in the driver IC may be very closely related to defects of the LCD.
To test such a driver IC, each test terminal of automatic test equipment (ATE) may be connected to a respective output pin of the driver IC so that the driver IC may be measured to determine whether the output signals from the driver IC are normal or abnormal. This conventional method using the ATE, however, may have a problem in that test terminals and test channels of the ATE may need to be provided in equal or greater number than the output pins of the driver IC.
FIG. 2 is a view illustrating a relationship of connections between an automatic test equipment (ATE) and a conventional gate driver to be measured by the automatic test equipment. Referring to FIG. 2, each of 2n output pins P0 through P2n−1 formed on the gate driver 10 may be respectively connected to each of 2n test terminals T0 through T2n−1 formed in automatic test equipment 20 so that the output signals from the output pins P0 through P2n−1 are measured by the automatic test equipment 20.
Conventionally, as illustrated in FIG. 2, in order to test a driver IC having many output pins, the test equipment may be provided with more test channels than output pins being tested.
However, such multi-channel test equipment may have a problem in that the test equipment may be expensive, because many difficulties may occur during production of the test probe cards.
In practice, a driver integrated circuit used in an LCD for mobile equipment may have 700 to 1,000 output pins. As a result, probe cards for the test equipment may be difficult to manufacture.
In addition, when dual tests to simultaneously test a dual chip are performed, 1,400 to 2,000 test channels may be required. In this case, the probe card in itself may not be manufactured and the aforementioned problems may become more serious.